Latex emulsions of resins may be produced using solvent-based phase inversion emulsification (PIE) processes in which resins are dissolved in a mixture of water and organic solvent(s) (e.g., methyl ethyl ketone (MEK), isopropanol (IPA) or both) to form a homogenous water-in-oil (W/O) dispersion (i.e., water droplets dispersed in continuous oil). Subsequently, water is added to convert the dispersion into a stable oil-in-water (O/W) latex.
Energy intensive processing of the latex then is used to remove virtually all traces of organic solvents, and finally surfactant and other preservatives may be added to provide a stable latex with relatively high solids content. Such latex may be used for many purposes including the application of Emulsion Aggregation (EA) methods for the production of toner particles (see, e.g., U.S. Pat. Nos. 5,853,943, 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210 and 5,994,020, and U.S. Pub. No. 2008/0107989, the disclosure of each of which hereby is incorporated by reference in entirety).
Batch processes use bulk materials (for example, about in volumes up to and more than 5,000 gallons) and are time consuming (for example, 25 hrs or more cycle time), labor intensive and have lot-to-lot variation. Further, one of the main PIE costs directly correlates with processing time, solvent distillation (˜18 hrs) being one of the more time consuming step, in which IPA removal, for example, is particularly difficult because IPA has affinity for water and can cause foaming. Significant amount of effort in speeding up the emulsification and solvent distillation processes has been applied with varying success.
Therefore, new emulsification processes, which provide both reduction in costs (on system simplification) and time savings (e.g., emulsification time and solvent distillation time), for latex preparation is highly desirable for overcoming batch process issues.